1. Field of the Invention
The invention relates to roll-on perfume compositions containing a cogeneric mixture of polyoxybutylene-polyoxyethylene block copolymers. These copolymers, containing internal polyoxybutylene hydrophobes, possess exceptional viscosity increasing ability when compared to previously available thickeners.
2. Description of the Prior Art
It is known to use certain nonionic surfactants in liquid, roll-on perfume compositions to aid in spreading of the essential oil on the skin so as to obtain a uniform coating. The surfactant in such compositions must actually perform several functions. First it must aid in spreading the essential oil and other ingredients on the skin so as to obtain a uniform coating. Second, it must stabilize the composition with regard to preventing separation of its components. Finally, it must increase the viscosity to such a degree that leakage from the container is minimized.
Polyoxypropylene-polyoxyethylene copolymers have been used in such compositions. In U.S. Pat. No. 4,089,814, for example, roll-on perfume compositions are disclosed which comprise water, an essential oil, an alcohol or other solvent, and a polyoxyethylene-polyoxypropylene block copolymer represented by the formula: EQU HO(C.sub.2 H.sub.4 O).sub.b (C.sub.3 H.sub.6 O).sub.a (C.sub.2 H.sub.4 O).sub.b H
wherein a is an integer such that the hydrophobe represented by (C.sub.3 H.sub.6 O).sub.a has a molecular weight of from 3250 to 4000 and b is an integer such that the hydrophile portion represented by (C.sub.2 H.sub.4 O).sub.b constitutes from about 50 to 90 weight percent of the copolymer. The average total theoretical molecular weight of the copolymers of use range from 6550 to 40,000.
The roll-on perfume compositions of U.S. Pat. No. 4,089,814 contain a minimum of 20 parts by weight of the above polyoxyethylene-polyoxypropylene block copolymer. Due to the expensive nature of these pharma-grade surfactants, compositions which minimize the amount of surfactant required, while maintaining or increasing the viscosity of the composition are desirable.